1. Field of the Invention
At least one embodiment of the present invention relates generally to removing undesirable constituents from fluid streams and, more specifically, to systems and methods for biologically and chemically treating gas streams.
2. Discussion of Related Art
Increased industrialization and population growth in urban settings over the past several decades have presented important environmental concerns. Significant design problems are associated with the purification and deodorization of effluent gas streams when public health and/or aesthetic considerations make it desirable to do so.
Various techniques have been developed in response to the need for removal of odorous constituents from effluent gas streams. As a general rule, an effective technique should be tailored to the particular compounds to be targeted. For example, in a sewage system environment, a primary cause of odor may be hydrogen sulfide. This compound is detectable by the human olfactory sense at very low concentrations. In addition to the unpleasant odor associated with it, hydrogen sulfide is noted for its toxicity and its capacity for corroding materials with which it comes in contact.
Hydrogen sulfide is not the only undesirable constituent found in effluent gases. Others, such as amines, mercaptans and organic acids can be produced from a variety of sources. Because of the undesirability of introducing such constituents into the atmosphere, communities and governmental agencies may formulate criteria for their regulation. A suitable gas treatment system, meeting such criteria, would substantially reduce the likelihood of any public nuisance or annoyance by removing, in a cost effective manner, substantial amounts of unwanted substances, preferably at or near the source of their production.
Removal of odorous constituents from a waste gas stream can be accomplished by several techniques. In the past, the treatment of polluted gases was performed mainly by means of chemical and physical processes. For example, processes involving incineration, absorption into a liquid phase, and adsorption onto a solid surface, such as activated carbon or charcoal, are well-established and reliable techniques.
Biological treatment has emerged as an alternative technology for odor control and has demonstrated an ability to successfully treat high flows of contaminated gas with high inlet pollutant concentrations. In such systems, a biomass of pollutant-degrading microorganisms is generally cultivated on the surface of media packing in a scrubber column. The conversion of pollutants to innocuous compounds is mediated by the microorganisms as the contaminated air is passed through the biological scrubber column.